Culicoides species as potential vectors of African horse sickness virus in the southern regions of South Africa

• Published in: Medical and veterinary entomology Vol. 33; no. 4; pp. 498 - 511
• Main Authors: Riddin, M. A., Venter, G. J., Labuschagne, K., Villet, M. H.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-12-2019; Wiley Subscription Services, Inc
• Subjects: Abundance; African horse sickness; African Horse Sickness Virus - physiology; Animals; Ceratopogonidae - classification; Ceratopogonidae - physiology; Climatic conditions; Culicoides; Epidemiology; Equidae; Female; Food Chain; Insect Vectors - classification; Insect Vectors - physiology; light trapping; Male; midges; Orbivirus; Seasons; South Africa; Species; Species Specificity; Surveillance; vector; Vectors; Winter; South Africa; light trapping; epidemiology; African horse sickness; Orbivirus; vector; midges; Culicoides
• ISSN: 0269-283X; 1365-2915
• DOI: 10.1111/mve.12391

African horse sickness (AHS), a disease of equids caused by the AHS virus, is of major concern in South Africa. With mortality reaching up to 95% in susceptible horses and the apparent reoccurrence of cases in regions deemed non‐endemic, most particularly the Eastern Cape, epidemiological research into factors contributing to the increase in the range of this economically important virus became imperative. The vectors, Culicoides (Diptera: Ceratopogonidae), are considered unable to proliferate during the unfavourable climatic conditions experienced in winter in the province, although the annual occurrence of AHS suggests that the virus has become established and that vector activity continues throughout the year. Surveillance of Culicoides within the province is sparse and little was known of the diversity of vector species or the abundance of known vectors, Culicoides imicola and Culicoides bolitinos. Surveillance was performed using light trapping methods at selected sites with varying equid species over two winter and two outbreak seasons, aiming to determine diversity, abundance and vector epidemiology of Culicoides within the province. The research provided an updated checklist of Culicoides species within the Eastern Cape, contributing to an increase in the knowledge of AHS vector epidemiology, as well as prevention and control in southern Africa.
The diversity and distribution of Culicoides in the Eastern Cape has changed, suggesting a previous underestimation and an epidemiological mechanism for endemic African horse sickness (AHS).
Under‐representation of proven vectors Culicoides bolitinos and Culicoides imicola compared with northern provinces, as well as the continuous presence of other orally‐susceptible species, is supportive of additional vectors contributing to local AHS virus persistence.
Based on abundance, C. bolitinos contributes most to vector epidemiology, with an apparent persistence of vectors throughout winter in the absence of an annual reintroduction from northern provinces, enabling endemic AHS.